I would like to suggest the use of "T-nuts" instead of the double hex nuts on this type of a modification. The advantage would be that a loose mounting screw could be tightened from the outside of the camera with out the need to hold the nuts inside the camera.

If T-nut is what I think it is (small nut with the pins / arms penetrating wood) then I am afraid they could cause some trouble to quite sensitive wood structure inside camera - wouldn't they?_________________Milos Gazdic | www.hirtc.com

That is something to be considered if the wood has become brittle with age. Another alternative with the same advantage would be to have a blackened brass plate about an eighth of an inch (3mm) thick with tapped holes matching the spacing of the holes in the strap lugs instead of the double nuts.

The miirror may collide with the flange of the T-nut, unless you grind
the flange where it may protrude into the mirroe area.
A better solution would be to use threaded inserts, press in or screw in
depending on the condition of the wood.

All these options require a much larger hole in the camera starting with the barbed insert which requires a hole 50% larger than the threaded fastener size it made for. 3 flute barbed inserts are worse for splitting the wood than 4 flute ones. They should screw in with a hex wrench. A T nut installed inside the body so that the strap lug screw pulls the chiseled spikes into the wood as the strap lug is tightened could work and the body length could be shortened but splitting the wood is a real possibility. A surface mount insert could be used from either the inside or outside and retained with #0, #1, or #2 flat head brass screws depending on the insert.

Painting a single machine nut once installed should seal and lock the threads preventing it from coming loose._________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.